That's wrong for OCaml programs, since strings in 32 bit OCaml
programs are limited to 16 MB (but effectively unlimited on 64 bit
platforms). So 64 bit should always be preferred. Having said that
we're still waiting for someone to port the OCaml compiler to
Linux/ppc64 ...

Ugh. You would have something different wouldn't you :/

Heh, right. But I bet this isn't the only case where 64 bit would
always be preferred. For example libraries which implement lightweight
threading often have seriously low limits on the number of threads
supported unless you use 64 bits, because each stack needs a sizable
piece of virtual address space (not real memory though). I don't think
you can make a hard rule that 32 bit userspace is always preferred.